Saturday, January 31, 2015

CDC Interim Guidance For Testing For Novel Flu

While the risk to the public remains low, the importation this month of two cases of H7N9 into Canada from China, the ongoing outbreak of H5N1 in Egypt, and the recent introduction of HPAI H5 viruses via wild and migratory birds into North America are all reasons why doctors around the country need to be aware of the potential for seeing novel flu cases.

The HPAI H5 viruses currently circulating in North America have not been associated with human infection - but they are related to H5 viruses that have - and so they are deserving of extra scrutiny and vigilance.

Background and Purpose

This document provides interim guidance for clinicians and public health professionals in the United States on appropriate testing, specimen collection and processing for patients who may be infected with novel influenza A viruses with the potential to cause severe illness in people. Examples of such viruses include Asian-lineage avian influenza A (H5N2), (H5N8), and (H5N1)1 viruses, which were detected in wild and domestic birds in North America in December 2014 and January 2015; these viruses may have some or all of their genes from Asian avian influenza viruses, but for simplicity will all be referred to as “newly detected avian influenza A H5” viruses in this guidance document. Other newly detected avian influenza A H5 viruses also may have the potential to cause severe disease in humans. For a list of avian influenza A H5 virus infections identified in birds in the United States, and their locations, please see an update on avian influenza findings maintained by the US Department of Agriculture. CDC will update this guidance as additional information becomes available.

The appearance of newly detected avian influenza A H5 viruses in North America may increase the likelihood of human infection with these viruses in the United States. Because these newly identified avian influenza A H5 viruses are related to avian influenza A viruses associated with severe disease in humans (e.g., highly pathogenic Asian-lineage avian influenza A (H5N1) virus), they should be regarded as having the potential to cause severe disease in humans until shown otherwise. Other CDC guidance provides recommendations for influenza viruses known to be associated with severe disease in humans.

1 The H5N1 virus isolated in the United States in January 2015 is a new mixed-origin virus (a “reassortant”) that is genetically different from the H5N1 virus found in several other countries (notably in Asia and Africa), which has caused human infections with high mortality. Although it is related to the H5N1 virus that has caused human infections with high mortality, the ability of this new reassortant H5N1 virus to cause severe disease is currently unknown.

Recommendations for Surveillance, Testing, and Investigation

Clinicians and public health personnel should consider the following recommendations for surveillance and testing:

Consider the possibility of infection with novel influenza A viruses with the potential to cause severe disease in humans in patients with medically-attended influenza-like illness (ILI) and acute respiratory infection (ARI) who have had recent contact1 (<10 days prior to illness onset) with sick or dead birds in any of the following categories2:

Domestic poultry (e.g., chickens, turkeys, ducks)

Wild aquatic birds (e.g., ducks, geese, swans)

Captive birds of prey (e.g., falcons) that have had contact with wild aquatic birds

If infection with a novel influenza A virus with the potential to cause severe disease in humans is possible, respiratory specimens should be collected with appropriate infection control precautions and sent to the state or local health department for immediate testing (see guidance below).

If infection with a novel influenza A virus with the potential to cause severe disease in humans is suspected, state health departments are encouraged to initiate a public health investigation with animal health partners and should notify CDC promptly.

2 For questions or concerns about possible human infection in patients with exposures to birds not listed here, please contact CDC. Exposures that occur in geographic regions in the United States where newly detected avian influenza A H5 viruses have been identified are of most concern.

When Specimens Should Be Collected

The duration of shedding of novel influenza A viruses in humans is largely unknown, and there are currently limited data describing prolonged shedding of people infected with these viruses. Therefore, the estimated duration of viral shedding is based upon seasonal influenza virus infection. Specimens should be obtained for novel influenza A virus testing as soon as possible after illness onset, ideally within 7 days of illness onset. However, as some persons who are infected with seasonal influenza viruses are known to shed virus for longer periods (e.g., children and immunocompromised persons), specimens should be tested for novel influenza A virus even if obtained after 7 days from illness onset. Note that prolonged shedding of influenza virus in the lower respiratory tract has been documented for critically ill patients with highly-pathogenic avian influenza A H5N1 virus and avian influenza A H7N9 virus infections.